Loop da Loop for my Rolling Ball Sculpture RBS4 EP 8 

I love that you show us the whole process of refinement.. even the initial 'fails'. Thank you for everything. So useful.

It has to be a 200mm vertical height diff, which is not the same as the length along the track. As you angle the 200mm long track further and further away from vertical, the height difference will go lower and lower. The final track angle looks to be about 45 degrees, so your height diff is closer to 140mm; this is why your diameter had to be so much smaller.

I'm about to make my first loop and I am doing some research. I think, similar to a roller coaster, loops are not circular in shape. So I may try a clothoid loop, which resembles an inverted tear drop and allows for less intense G-forces throughout the element. The teardrop design makes it much easier to balance these forces.

When making the loop I think if you reduce the track width in the loop it will reduce friction caused as the forces on the balls try to spread the track as they take the loop. Also slightly cuts down on the helix require for the exit to miss the entry (Just a thought)

I'm a retired aerospace engineer, and I spent a few years after I retired designing and building backyard roller coasters with my grandkids. I looked at a loop, and did the calculations in a spreadsheet. I made a video about loops and put it on my RU-vid channel, but never made a loop, as the forces and accelerations were too high for my little grandkids. I documented all four of my backyard roller coasters in videos on my channel, and wrote two ebooks I'd be glad to gift you if you contact me. You point out that your coaster, in practice, needed a lot higher hill than the physics equations predicted. I suspect that when the ball is in the loop and under high centripetal acceleration forces (a = v^2/r), they are high enough to spread the track rails and you get extra mechanical friction. You might try more cross ties so the track is stiffer and see if it goes faster? Plus, aerodynamic drag goes up with velocity to the 3rd power, but it's a sphere so the air friction should be low. I believe that once you can characterize your ball drag on a track as a function of speed and accelerations, you could predict with some accuracy your performance before you build. I have a spreadsheet which does this, I'd be glad to share it. I think it is still available for free at backyardrollercoasters.org. And a clothoid loop, with large radius at the run-in and run-out, and smaller radius at the top, will work better than a single radius loop. You need upwards force at the top of the loop, and a smaller radius will increase that centripetal force. I just bought the equipment on on of your videos, and hope to get into this fascinating hobby. Thanks for the videos and instruction.

Brilliant

I think one thing that may alter your (probably not incorrect) math is the fact that the ball is not rolling on a planar surface - as I am sure that formula was calculated for. The slight lowering of the ball in the tracks will lower the initiation height a bit, and then you add to it whatever frictional losses from the rails are... (I wonder if that formula considers aerodynamic losses as well?) It might be interesting to see if a slightly larger diameter glass marble would do any better or worse. Since it weighs less it should deform the rail material less and roll a bit easier, as well as sitting higher on the track for a bit more speed. Edit: Listening to the vid again, it sounds like friction was considered...

I believe the problem of your calculation is, that you did not include the inertia and angular kinetic energy. As some of the initial potential energy will be stored in angular kinetic energy, the loop has to be smaller than what you would expect for an object, that is merely sliding in the loop. I might make the calculation later, as I also want to make a loop for a marble machine at some point. If I do, I will share the result with you for later reference :)

Have you attempted a corkscrew type loop?

Fascinating! I tried making the same after watching your video with similar results. Are you twisting the track in a drill to straighten it out before bending it to create the loop? Or is your loop track not twisted? Do you think that twisting the track would impact the amount of friction? I’d like to re-try this without twisting the track but haven’t found the time.

Just a thought, would reducig the track width for this sectio help to reduce friction, allowing for a bigger loop/shorter run in?

So exactly what terms do you search for when seeking formulas such as this? Got lots more questions, but what you're doing is pretty sweet! Can't wait to try my hand at one of these!

Hello, I was wondering about your math. Can it be so much off? Including the ball rotation energy into the equation does not change the drop height by magnitudes. Is you track spacer doing something with the ball? I immagine to see the ball always stop when it reaches the track spacer. 3:50 and 4:58 drop of the ball right at the track spacer? coincidence?

which soldering tool do you use?

What type of soldering iron do you use. Thanks